Disposable products such as facial tissue, bath tissue, paper towels, and the like are typically made from one or more webs of paper. If the products are to perform their intended tasks, the paper webs from which they are formed must exhibit certain physical characteristics. Among the more important of these characteristics are strength, softness, and absorbency. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation the user perceives as the user crumples the paper in his or her hand and contacts various portions of his or her anatomy with the paper web. Softness generally increases as stiffness decreases. Absorbency is the characteristic of the paper web which allows it to take up and retain fluids. Typically, the softness and/or absorbency of a paper web is increased at the expense of the strength of the paper web. Accordingly, papermaking methods have been developed in an attempt to provide soft and absorbent disposable paper products having desirable strength characteristics.
U.S. Pat. No. 3,301,746 issued to Sanford et al. discloses a paper web which is thermally pre-dried with a through air-drying system. Portions of the web are then imprinted with a fabric knuckle pattern at the dryer drum to yield paper having two distinct regions of differing fiber density. Through air drying typically improves both the softness and the absorbency of a paper web. Disposable paper products made using such paper as a substrate have enjoyed wide commercial success.
U.S. Pat. No. 4,637,859 issued to Trokhan also describes a paper having two distinct regions. The first, the network region, forms an essentially continuous pattern. The other region comprises a plurality of discrete domes. The network region completely encircles the domes and isolates one dome from another. The network region has a relatively high density while the domes have a relatively low density. Paper made according to U.S. Pat. No. 4,637,859 exhibits good absorbency, softness, tensile strength, burst strength and bulk. Depending on the pattern chosen for the network region the paper also has the ability to stretch in the machine direction, the cross direction, and in intermediate directions even in the absence of creping. Paper of this type has enjoyed wide commercial success as a substrate for paper toweling and as bath tissue.
An alternative approach to improving the properties of disposable paper products has been to incorporate non-cellulosic materials into the structure of the disposable paper product. For example, the use of scrims to add strength to disposable paper products is well known in the art. Also, non-cellulosic fibers have been added to the furnish for the papermaking machine used to produce the substrate for the disposable paper product. However, approaches of this type also carry a cost such as loss of softness or loss of absorbency. Typically, the art has only used such approaches to meet very specific needs, where the benefit gained outweighs the cost paid.
Frequently, disposable paper products, particularly paper towels, comprise a laminate of two or more laminae. Disposable products comprising more than one lamina have the desirable properties of increased bulk, increased absorbency and increased strength per unit area of product compared to products comprising a single lamina.
U.S. Pat. No. 3,414,459 issued to Wells describes a laminated paper product formed by embossing identical raised patterns of protuberances on two paper sheets and adhesively joining the mated distal surfaces of the protuberances to form the laminate. Laminates of this type have enjoyed considerable commercial success, particularly as disposable paper toweling.
U.S. Pat. No. 4,978,565 issued to Pigneul, et al. describes lamninated paper products that are adhesively joined, at least partially, by means of protruding elements. The elements are said to be positioned according to lines or combinations of lines which reproduce spaced motifs. Laminates of this type are said to provide a satisfactory bulky texture without a reduction in mechanical strength which is said to come from embossing to a high density of protuberances.
U.S. Pat. No. 5,294,475 issued to McNeil describes embossed paper laminates of two paper lamina wherein each embossed site of one lamina is adhesively joined to the nonembossed region of the other lamina. Laminates of this type have a high quality quilted cloth-like appearance, a relatively thick caliper and in aesthetically pleasing pattern without sacrificing other desirable qualities such as softness, absorbency and bond strength between the laminae.
While the art has continually worked to improve the properties of disposable paper products without loss of other properties, users of such articles frequently find it difficult to recognize such improvements. For example, when an embossed disposable paper product of the present art is saturated with water all patterned appearance coming from such embossments essentially disappears. This means, even if the embossing pattern were chosen to preserve the physical properties of the unembossed paper to the greatest degree possible, a user of such a product would have no readily discernible signal that the product provided such benefits.
Thus, it is an object of the present invention to provide disposable products, such as paper toweling, with a readily recognizable signal that the article has desirable physical properties, both when the article is dry and, particularly, when the article is wetted with a substantially transparent aqueous liquid. It is a further object of the present invention to provide laminated disposable products such that the difference in visual appearance of the paper webs that comprise the laminae and the visual appearance of an indicator means is sufficiently great, when the laminated disposable paper product is wet, to provide such a readily discernible signal.